Anorexia nervosa and bulimia seem to arise out of nowhere. Typically observed in girls, these are psychiatric disorders that are often mystifying to family and friends as obsession about food intake and avoiding food begins to overtake a previously normal life.

Both eating disorders are on the rise. The current incidence of anorexia nervosa in adolescent girls is estimated to be about 0.5%, while 1% to 5% of adolescent girls develop bulimia. Although these percentages may seem modest, they actually reveal that these serious conditions are hardly unusual.

The causes of anorexia nervosa or bulimia are unclear, but both involve a distorted self-perception. When a teenager with anorexia nervosa looks in the mirror, she sees something different than what anyone else sees. Rather than a young, healthy woman, she perceives an unacceptably fat girl that needs to lose weight urgently. In an attempt to shed that fat, she reduces her diet to almost nothing, obsessing even about the few calories she does ingest. Indeed, it is common for the girl with anorexia nervosa to count the calories of everything she eats, weigh the food, and then exercise compulsively to burn the energy she consumes. And although she might loose her hair, miss her period become sensitive to cold, slow her heart, feel fatigued, dizzy and constipated, she still does not feel thin enough.

Bulimia is somewhat different. Instead of dieting obsessively, bulimics often eat a huge amount of food and then become guilty or depressed, seeking to rid the calories by inducing vomiting or taking laxatives. Unlike girls with anorexia nervosa, who are always thin, bulimics may or may not have substantial weight loss, but they often suffer from electrolyte disturbances, gastrointestinal bleeding, muscle weakness, and dehydration. They are also often depressed.

Eating disorders are thought to be particularly common in teenagers because of the changes in body type that take place at this time. Between the ages of 11 and 14 hormonal changes erupt, creating new shapes and unleashing feelings over which teens have little control. It is believed that those predisposed to eating disorders attempt to control their body fat as a surrogate for mastering the rapid and confusing changes in their lives. With the characteristic desire for privacy experienced by many adolescents, many teens try and often succeed in hiding this disorder from their family for months or years. Characteristically, they are unable to admit even to themselves that they have a problem.

Although eating disorders are often based on advertising and other mediators of modern culture that equate thinness with desirability, studies show that these tend to be familial. No social strata or ethnic group is insulated. However, certain familial patterns of behavior, such as using food to reward or punish or sending strong signals of approval for thinness, appear to be contributory. Those at highest risk appear to be those with low self-esteem, depression, obsessive behaviors, desire for perfection, or history of abuse. It has also been shown that the incidence of eating disorders is higher in teenagers who participate in activities that emphasize a thin physique such as dance, gymnastics, skating or diving.

With comprehensive treatment most teenagers can be relieved of the symptoms of eating disorders. Generally, a team approach is employed that includes the primary care physician, a nutritionist and a psychiatrist or psychologist. The role of the psychiatrist or psychologist may be critical in the large proportion of teens with eating disorders who suffer from concomitant issues of depression, anxiety, and substance abuse.

Parents often ask how to identify symptoms of eating disorders, which is a highly relevant question given research that shows early detection and treatment leads to more favorable outcomes. The danger signs are excessive weight loss, social withdrawal, preoccupation with being fat, and the loss of menses. Although family environment is not always a contributing factor to the development of an eating disorder, the comprehensive, long-term treatment plan may involve participation of the whole family. It is important to recognize that a restoration to normal eating behavior may involve long-term treatment, but the good news is that comprehensive care and a supportive family can be effective.

Amy Glaser MD, a mother of two teenage boys, has a private adolescent practice at 430 West Broadway, 212-941-1520. She can also be reached at aglasermd@aol.com